This invention relates generally to support structure in a tumbler-style washing machine. More specifically, the invention pertains to the type of washing machine having an elongated rotatable tubular drum adapted to rotate about a horizontal axis, and a bearing support system for the drum which includes a number of buffers distributed along its length.
When a washing drum is secured to fixed support structure or to a bearing system originally secured to such structure, the bearing forces of the individual buffers may vary, both during idle periods and due to motion during operation, owing to the distribution of the mass of the drum, inaccuracies in manufacture, varying loads and changing tolerances between components which result through prolonged use. Such varying forces will vary even when the mass distribution of the drum is substantially uniform, or at least periodically uniform and even when the bearing points are distributed substantially uniformly along the drum, allowing for the existing mass distribution. Such variations in bearing forces whether occurring regularly or irregularly during operation, are extremely undesirable.
For example, if a tubular, rotatable drum is suspended to rotate about its longitudinal axis by means of a number of bearings, and, if required, driving elements such as chains or the like, each chain being guided around the surface of the drum and over a pulley disposed about the drum, variations in the load on the chains may frequently result in breakdown. Such breakdown may be due to the fact that the drum, which is usually welded from relatively thin sheet metal, will flex and distort relatively easily. This may be particularly true where the drum is substantially long (12 meters or more) and/or has a relatively small diameter. In addition, in the manufacture and assembly of such a drum, the intended round or tubular configuration may not be achieved since individual drum segments may become radially displaced during assembly such that parts of the drum are disposed eccentrically to the drum axis.
As a result of such factors, the chains or other bearing elements, even though uniformly spaced along the drum, may be subjected to greatly varying loads and the loading conditions will vary continuously during operation.
Under unfavorable circumstances, it may also happen that only a few in a plurality of bearing chains will actually bear a load, at least for a time, with the other chains in the plurality being subjected to little or no load. This overstressing of a few of the bearing elements will quite often result in breakdown. In order to avoid such damage, the chains or other bearing elements must be made considerably oversized. This, however, will result in very heavy and expensive chains or other bearing elements and will also result in the undesirable need for operatively associated elements, such as drive pulleys, of unreasonably cumbersome size.
In order to avoid or largely reduce the aforementioned disadvantages and to absorb or attenuate the impacts or similar stresses resulting therefrom or caused by external factors (such as the motion of the articles being treated during the washing and conveying process) it has heretofore been proposed that the pulleys for guiding the chains or the like should each be held on a substantially horizontally extending rocker beam element which projects generally transverse to the longitudinal axis of the drum, and that one end of the rocker be made pivotal about a horizontal axis while the other end is resiliently borne by a buffer in the form of a rigidly mounted spring. Such a bearing system can reduce the effect of non-uniform stressing of the chains or the like caused by inaccuracies during manufacture, but it does not achieve uniform distribution of stress on the chains during operation. Another disadvantage of this system is that the springs have to be individually adjusted by hand and readjusted by hand after the inevitable stretching of the chains during operation. Even when such laborious adjustment has been performed, the uniform stress placed on the chains is immediately lost when the drum has rotated through a fraction of a complete revolution due to the inaccuracies heretofore described with regard to manufacture and assembly of the drum. More specifically, departures from roundness and the radial offset of the individual segments will destroy any uniformity of stress distribution as soon as the drum is partly rotated away from the position in which the adjustment was made. Moreover, the known system heretofore described cannot be utilized for adjusting the level of the drum, though the ability to make such adjustment is very desirable.